The invention is directed to a process for improving mineral asphalt coatings for streets and roadways, i.e., pavements.
The development of street traffic in the last twenty years has brought about significant changes. A steadily increasing passenger automobile traffic coincided with a growing heavy load traffic. The heavy load traffic was still carried by the trend "go to the road" so that particularly high growth rates of the loaded transport on the streets has been achieved. An end of this development is not yet seen, especially since the building of vehicles presents always larger transport vehicles. The heavy load of the streets often leads to strong appearances of wear in very short times. The repairs needed as a result and the needed reconditioning yearly cost large sums of money.
As a result of the high loads or insufficient stability, crumblings and grooves are observed in the street coating. In summer, the street surfaces warm up to considerable temperatures. Because of their thermoplastic properties, the binding agent becomes pliable and spreads. If the asphalt coating then lacks the so-called inner hollow space, the bitumen or the tar mass with a part of the mineral fine portion enters the surface. The reconditioned portion of the asphalt coating changes because simultaneously the fine gravel portion is pressed downwardly by the load. On the surface of the asphalt coating there continuously appear growing specks. One then speaks of the so-called "sweating". Grooves and crumblings particularly in curves occur. Both phenomena are sources of danger which problematically can be present with the wetness (aqua-planning) that occurs. In winter, the asphalt becomes brittle as a result of which the low grade asphalt which, because of their mineral properties, cannot take up high amounts of binder, are endangered. The cold embrittlement leads to the loosening of the finely ground particles, surface damage and quicker abrasion or wear. In such cases, one speaks of the "deterioration" of the asphalt coating. These surfaces offer salt strewn on the street good places for attack so that frequent repair of the binder layer of the street surface is necessary.
For a long time efforts have been made to be able to use these expensive capital investments for a longer time. The forbidding of spiked tires is understood from this point of view. The development of high quality and especially durable street coatings represents the ample and important alternative.
Street construction materials improved by additives can delay the wearing out and increase the carrying capacity. Known additives are especially asbestos fibers and asbestos flour/synthetic resin granulates and liquid synthetic resin components as well as pulverized waste materials as for example "red filler" from the recovery of aluminum. The asbestos in part produces quite usable results. However, in the future, this must be given up because this additive appears to be injurious to the health. Synthetic resins products do not always satisfy the requirements or must be supplied in too large proportions so that there is a drop in the economy of the product. In the mixing process of the asphalt coating materials themselves also an addition of certain materials frequently does not permit the necessary temperatures.